New Optical Sensor Device Designed to Detect Drugs, Bomb-Making Chemicals

Researchers searching for bomb-making components, traces of drugs and other chemicals time and again shine light on the materials they are examining.

The image above depicts a new device for surface enhanced infrared absorption spectroscopy. Infrared light (the white beams) is trapped by tiny gaps in the metal surface, where it can be used to detect trace amounts of matter. (Credit: University at Buffalo.)

This technique is known as spectroscopy, and it includes examining how light interacts with trace quantities of matter.

Infrared absorption spectroscopy, one of the more effective types of spectroscopy, is used by Researchers to detect performance-enhancing drugs in blood samples and miniature particles of explosives in the air.

While infrared absorption spectroscopy has improved significantly in the last century, Researchers still continue working on making the technology more sensitive, affordable and versatile. A new light-trapping sensor, built by a University at Buffalo-led team of Engineers and described in an Advanced Optical Materials study, shows progress in all three areas.

This new optical device has the potential to improve our abilities to detect all sorts of biological and chemical samples.

Qiaoqiang Gan, PhD, Associate Professor of Electrical Engineering in the School of Engineering and Applied Sciences at UB and Lead Author of the study

The study’s Co-authors in Gan’s lab include Dengxin Ji, Alec Cheney, Nan Zhang Haomin Song and Xie Zeng, PhD. Additional Co-authors come from Fudan University and Northeastern University, both in China, and the University of Wisconsin-Madison. The study will be featured on the cover of September’s Advanced Science News.

The sensor functions with light in the mid-infrared band of the electromagnetic spectrum. This part of the spectrum is utilized for most night-vision, remote controls, and other applications.

The sensor has two layers of metal with an insulator placed in between. Using a fabrication method called atomic layer deposition, Researchers built a device with gaps less than five nm (a human hair is about 75,000 nm in diameter) between two metal layers. Notably, these gaps enable the sensor to absorb nearly 81% of infrared light, a great improvement from the 3% that similar devices absorb.

The process is referred to as surface-enhanced infrared absorption (SEIRA) spectroscopy. The sensor, which serves as a substrate for the materials being inspected, increases the sensitivity of SEIRA devices to detect molecules at 100 to 1,000 times better resolution than earlier reported results.

The increase makes SEIRA spectroscopy similar to another type of spectroscopic analysis, surface-enhanced Rama spectroscopy (SERS), which measures light scattering rather than absorption.

The SEIRA advancement could be beneficial in any scenario that requires detecting traces of molecules, says Ji, the First Author and a PhD Candidate in Gan’s lab. This includes but is not limited to bomb-making materials, drug detection in blood, tracking diseases and fraudulent art.

Researchers plan to continue the study, and investigate how to integrate the SEIRA advancement with innovative SERS.

The U.S. National Science Foundation’s Nanomanufacturing program, the National Science Foundation of China and the Chinese Scholarship Council supported this research.

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